Caseous Calcification of the Mitral Annulus

Caseous calcification of the mitral annulus (CCMA) is a rare variant of mitral annular calcification (MAC) usually described as an antemortem finding. We report a case of sudden cardiac arrest in a 39-year-old male with end-stage renal disease undergoing hemodialysis with a history of Fabry disease by kidney biopsy. Autopsy revealed significant circumferential annular calcification in both mitral and aortic valves with a caseous gross appearance. Histologically, these areas consisted of amorphous basophilic material accompanied by a surrounding granulomatous-appearing infiltrate. Von Kossa staining on non-decalcified tissue revealed strong positive staining, confirming CCMA diagnosis. While identifiable, the atrioventricular node was displaced and distorted by caseous deposits. Toluidine blue staining of myocardium showed osmophilic accumulations, and electron microscopy (EM) showed myeloid/zebra bodies, consistent with Fabry disease. We posit that Fabry disease leads to end-stage kidney disease, altering calcium phosphate metabolism, a proposed mechanism for CCMA. This case highlights the multifactorial nature of sudden cardiac death in decedents with various structural cardiac changes and potential renal-disease-induced electrolyte imbalances. We aim to bring awareness to this rare entity, its potential role in a sudden cardiac death, and to highlight the need to use non-decalcified tissue when staining for calcium to establish the diagnosis.